1. The Field of the Invention
The present invention relates to medical devices that can be placed in bodily conduits. More specifically, the invention relates to balloons and catheters using such balloons for administering treatments to widen constricted passages, deliver therapeutic agents, deliver endoprosthesis' or perform other medical procedures.
2. The Relevant Technology
Balloon catheters are well known for their utility in medical procedures. Typically, balloon catheters have a balloon fastened at least at one end around the exterior of a hollow catheter shaft. The hollow interior of the balloon is in fluid flow relation with the hollow interior of the shaft. Fluid under pressure can be supplied to the interior of the balloon through the shaft to expand the balloon against an obstruction.
Presently catheter balloons may be classified as compliant, semi-compliant, or non-compliant balloons. Compliance can be defined as the increase in diameter from nominal balloon pressure to rated burst pressure. Non-compliant balloons have less increase in diameter, than semi-compliant balloons, which in turn have less increase in diameter than compliant balloons.
Compliant balloons expand and stretch with increasing pressure within the balloon, and are made from such materials as polyethylene or polyolefin copolymers. Non-compliant balloons, made from such materials as polyethylene terephthalate (PET) or polyamides, remain substantially at a preselected diameter as the internal balloon pressure increases beyond that required to fully inflate the balloon.
Compliant balloon materials provide a degree of softness to the balloon which aids its passage through, e.g., blood vessels with minimal trauma. Known compliant balloon materials also can display good abrasion and puncture resistance at thicknesses typically used for medical device balloons. However, as mentioned above, they do not remain at the desired diameter with increasing pressure. Such compliant balloons also lack sufficient hoop strength to achieve high dilating forces.
A non-compliant balloon, that is one remaining at a preselected diameter regardless of increasing pressure, is often desirable. Typical non-compliant balloon materials do not exhibit the same degrees of softness and abrasion resistance as the compliant balloons.
It would be desirable, for many treatment conditions, to have a dilatation balloon exhibiting the combined characteristics of softness, abrasion and puncture resistance, hoop strength, and the ability to maintain a preselected diameter as the internal pressure within the balloon is increased. The balloon described herein was developed to address that need.